Selectable valves are frequently used in applications which involve hydraulics, pneumatics, and pyrotechnics. Typically, a single inlet may be selectively switched between multiple outlet ports by displacing a translatable valve spool. A typical application is in the field of pyrotechnic pilot seat ejection from a military aircraft. For example, with the valve spool positioned in a first location, the first occupant's seat ejection mechanism will be effected. If the valve spool is displaced to a second position, the inlet pyrotechnic charge flow is diverted thereby enabling seat ejection for a second aircraft occupant. Accordingly, the same valve may be used for sequentially ejecting two seats.
O-ring seals are frequently used at the sliding seal interface between a valve spool and a poppet. In the case of pyrotechnic applications, high dynamic flow and repeated use cause rapid deterioration or damage of such seals, thereby shortening the useful life of the valve. Further, such high dynamic loads tend to induce reaction forces on the poppet, which prevents it from providing a continuous intimate seal with the spool.